Interchangeable facing and backing



Patented Nov. il,

Tl'llAS 0F- COLUMBUS, COHIE, ASSGR T@ THE @@MEUS Dmlullli i MANUFACTURENG GOMANY, @13" GUL'MBUS, @REQ XNTERCHANGMBLE FCENG AND BCKNG.

Application led September 13, le20. Serial llo.

To all whom t may concern Be it known that l, lHoMs STEELE, a citizen of the United States, residing at rColumbus, in the county of Franklin and State of Ohio, have invented certain new and useful tmprovements in Interchangeable Facings and Backings, of which the following is a specification. i

Considerable difficulty has been experienced in the manufacture of interchangeable tooth facings to secure a firm anchor between the facing and backing and at. the same time prevent the anchor on the backing from showing through the translucent' body. Posts or anchors of material cross sectional arca have been used but this is objectionable -in that the perimeter of the post lies too close to the surface of the tooth and it is also objectionable in that it very materially weakens the porcelain.

Theobject of my invention is to position the post a greater distance from the backing than has heretofore been thought practical and l accomplish this by making the web between the post and backing wider, and by flattening or increasing the arc of the post l secure a larger area of anchorage between the facing and backing and at the same time am enabled to space the perimeter of the post sufficiently far'from the outer surface of the tooth to prevent it from showing through the translucent body.

A further object of my invention is to so construct the post of the backing that l am enabled to run or extend the post relatively nearer vthe incisal edge than has heretofore been deemed practical, and at the same time prevent it from showing through Y. rthe translucent body, whereby l addk resistance and strength to the denture by supporting it in this manner; and with these and other objects in view my invention consists of the parts and combi-nation of parte as will be hereinafter pointedout.

ln the drawings:

Figure l is a vertical longitudinal section of a tooth facing embodying my invention.

Figure 2 is a similar view of the facing mounted on a backing.

Figure 3 is a transverse sectional view of the facing on the line 3-3 Figure l.

Figure d is a transverse sectional view on the line i4-4 Figure 2.

. Figure 5 is a front elevation of my improved backing and post.;

Figure 6 is a side elevation of Figure 5.

Figure 7 is a sectional view'on the line 7 7 Figure 5.

Figure 8 is a detail sectional view.

rllhe facing and backing herein disclosed is primarily intended for accurately interchangeable teeth and is an improvement on the interchangeable teeth heretofore patented by me. y

rlhe reference numeral l designates a orcelain facing which is molded with a ongitudinally extending bore 2 parallel with the lingual side of the facing, one wall of the bore at 3 being bevelled on an angle toward the lingual side of the facingwhereby the bottoni of the bore 2 terminates in a very blunt and squared point as at t while the side walls converge as at 3a Figure 8. A. passageway or slot 5 extending into the facing from the lingual side communicates with the bore 2 and is provided at its lower end with an abutment or shoulder 6 materially above the lower end of the bore 2 inasmuch as the slot ti is not as long as the bore 2. Both the slot 5 and bore 2 extend upwardly through the gingival end of the facing. lt will be noted that the convergy ing walls 3a and the bevelled end 3 of the bore all diverge from the outer surface of the tooth.

The biscuit thus molded is baked in a very high temperature and is subject to warping strains and stresses,therefore after such baking it is necessary, in order 'that the facings be accurately interchangeable that the lingual side of the facings, and the walls of the slot be ground. This grinding process is a very difficult one but l have designed tools anddevices to accurately accomplish the saine whereby l are. enabled to grind the lingual face to a perfect plane, accurately grind the walls of the slot so that each `tooth made is accurately interchangeable with another, whereby upon fracture or damage to a facing another facing may be readily substituted without removing the bridge or changing the backing and post.

lt will be noted that' by reason of the particular formation of the slot and bore, especially the bore in the facing, lt am enabled to space the post a greater distance from the backing whereby l can position a greater bulk of porcelain between the ost and backing than is ossible with teet n as heretofore constructe one'. at the saine time lll@ lilo

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, bottom edge l() of the web 9 and said bottom edge 10 rests on the shoulder or bottom wall l1 of the slot 5 so that the facing through the blunt bottom 4 of the bore and the com paratively wide shoulder 5 ofl the slot has a material bearing to resist the strains and stresses imposed upon it incident to mastication and by reason of this distribution of stresses and strains and the large amount of porcelain between the bac-king plate '7 and post 8 the facing is much stronger and very materially less liable to split or fracture.

The increased arc of the outer face of the post with the substantially inner face of the post 8 enables me to putl a. comparatively large amount of metal -in the post, increases the bearing area of the post in the facing thereby distributing the strains and stresses throughout a larger area of the facing which practically eliminates the possibility .of the splitting or fracture of the facing. At its lower end the side walls of the post converge as at 1l and the inner or arcuate/face of the post converges toward the backing as at 12, the lower end of the post being "blunt as at 13, all configuration of the post conforming to the formation of the bore 2; The converging faces l1 and 12 inclining away from the surface of the facing thus enabling me to extend the post closer to the incisal edge than has heretofore been pos` sible and lat the same time not show through the translucent ,body thereby enabling me to obtain maximum strength in the structure Without sacrificingthe appearance of the facing. In other words by extending the post to a point relatively lower than present day practice, l add resistance and strength to the denture by supporting it in this manner, namely tov a point relatively nearer the ineis'al edge than is now deemed practical by any present form of construction, and the comparatively largeramount of porcelain between the lingual side and the under face of the post also materially increases the strength of the facing transversely.

Changes maybe made in the details of construction for anterior and posterior fac` ings'within the scope of the claims.

4Whatlclaim is:

l. A backing for a facing having a post and a web connecting the post to the backing, the outer perimeter of the post converging at its lower end portion towards the backing. l

2. A backing for a denture having a post the outer face of which is converged towards the backing at its lower end portion, and a wide web connecting the post for a portion of its length to and spacing it wide from the backing above said converging end.'

*3. A backingrfor a tooth comprising a flat plate, a wide web extending from and at right angles to said plate, and extending from the gingival end of the plate to a point short of the incisor end of the plate, a post longer than and secured to said web and having its outer and side faces, at the lower end portion below the web,l converge toa blunt point.

.4. A facing having a 'longitudinal bore extending from the gingival end toward the incisal edge and parallelwith thelingual Side, and spaced a wide distance from the lingual side7 a widev slot extending from the lingual side and communicating with said bore, the outer wall of the bore, below the bottom of the slot, converging toward the lingual side.

5. A facing having a longitudinal bore extending from its gingival end, the front and side faces of which converge at the lower end of the bore, said bore being spaced a material distance from the lingual side, and a slot in the lingual side communicating with said bore above the converging end of the bore and of less length than the bore.

6.l An interchangeable facing having a longitudinal bore extending from the gingival end to a point closevto the incisal edge with its longitudinal axis substantially midway between the lingual side and the labial face, the face. of the front wall of the bore, near its lower end, being converged toward the lingual side, whereby a maximum amount of material is maintained between the labial face of the tooth and the converging outer face of the bore, and a slot in the lingual side communicating with but shorter than the said bore. 

